Technical Field
This invention relates generally to a Global Navigation Satellite System (GNSS), and more specifically to a system and method for detecting false GNSS satellite signals, and for determining the direction of the transmitter of the false GNSS satellite signals.
State of the Art
Global Navigation Satellite Systems are in widespread use to determine the location and/or attitude of a body. A GNSS includes a network of satellites that broadcast GNSS radio signals. GNSS satellite signals allow a user to determine, with a high degree of accuracy, the location of a receiving antenna, the time of signal reception, and/or the attitude of a body that has a pair of receiving antennas fixed to it. Location is determined by receiving GNSS satellite signals from multiple satellites in known positions, determining the transition time for each of the signals, and solving for the position of the receiving antenna based on the known data. The location of two or more receiving antennas that have known placements relative to an object can be used to determine the attitude of the object. Examples of GNSS systems include Navstar Global Positioning System (GPS), established by the United States; Globalnaya Navigatsionnay Sputnikovaya Sistema, or Global Orbiting Navigation Satellite System (GLONASS), established by the Russian Federation and similar in concept to GPS; the BeiDou Navigation Satellite System (BDS) created by the Chinese; and Galileo, also similar to GPS but created by the European Community and slated for full operational capacity in the near future.
The GNSS is used extensively to navigate vehicles such as cars, boats, farm machinery, airplanes, and space vehicles. A problem is that ‘false’ GNSS signals can be used to ‘spoof’, or trick, a GNSS navigational system into straying off course or to provide an inaccurate time. Sophisticated GNSS spoofing systems can be used to take control of a navigational system and reroute a vehicle to an unintended location. Spoofing systems can be used for malevolent purposes—to steal, harm, reroute, or destroy important vehicles and machinery, or to allow false transactions to occur. Thus, what is needed is a system to detect the presence of false GNSS satellite signals. Once the presence of false GNSS satellite signals is detected, the navigational system can be prevented from being influenced by the false GNSS satellite signals. Also needed is a system and method for determining the direction of the false GNSS satellite signal transmitter. Knowing the direction of the false GNSS signal transmitter will aid in disabling the device.